in - The label value is one of a set of given values.!= - The label value is not equal to a given value.= - The label value is strictly equal to a given value.= - The label value is equal to a given value.These include equality-based and set-based comparisons: Label-based queries support several kinds of comparison operator. You can use a form of selector to filter the objects that are returned by Kubectl: These will be matched by the selector so they become part of the Deployment. The Deployment's template will create Pods that have the /app label set. Labels possess the same constraints around key names and prefixes. Add a labels field to the object's metadata, then populate it with key-value pairs. Labels are attached to objects in the same way as annotations. Node-environment: production Setting Labels Here's a Pod which selects Nodes that have the node-environment: production label: This is a key difference compared to annotations which aren't supported as selectors. Labels can be used as selectors when referencing objects. You might use labels to denote a resource's release status (such as beta or stable) or the development stage it maps to ( build or qa). They're commonly used to represent processes and organizational structures. Whereas annotations are intentionally purposeless, capable of representing any arbitrary data, labels are meant for more formal situations. The documentation describes the role of labels as "identifying attributes of objects that are meaningful and relevant to users" but independent of the properties of the core system. Labels are another form of metadata which you can attach to your resources. It must start and end with an alphanumeric character. The key needs to be 63 characters or less and can include alphanumeric characters, dashes, underscores, and dots. Setting AnnotationsĪnnotations are defined as part of a resource's metadata field. The model lets you store useful data directly alongside your objects, instead of having to refer to external documentation or databases.
As long as your data can be expressed as a key-value pair, you can create an annotation that encapsulates it.
There's no restrictions on what you use annotations for. You could use them to add information about the tool that created an object, define who's responsible for its management, or add tags to be picked up by external tools. This means annotations are best used for data that's independent of the object and its role in your cluster. Their status as "non-identifying" means they aren't used internally by Kubernetes as part of its object selection system. This usually consists of machine-generated data, and can even be stored in JSON form.The Kubernetes documentation defines annotations as "arbitrary non-identifying metadata" which you add to your objects. The reason why labels are used as selectors as opposed to annotations is because most Kubernetes implementation index labels in etcd.Īnnotations are used to store data about the resource itself Merge and stream logs of the various pod that share the same label Nonidentifying information that can be leveraged by tools andįind all pods that have a value associated with the key Resembles labels: annotations are key/value pairs designed to hold Provide the foundation for grouping objects.Īnnotations, on the other hand, provide a storage mechanism that They can be arbitrary, and are usefulįor attaching identifying information to Kubernetes objects. Labels are key/value pairs that can be attached to Kubernetes objects My understanding is rather limited here, however reading the official docs has not really helped me understand the use case of when do I use annotations vs labels. When do we use annotations over labels and vice-versa? What are the pros and cons of each? Is this right? If this is so, then what is the practical use of annotations? Is it something to do with performance? Where labels are under the scanner of Kubernetes for filters and annotations are purely for adding metadata that is just informational?īut I've seen in cases where deployments needing Nginx or ingress capabilities using annotations. Labels on the other hand are metadata key-value pairs that can be used by Kubernetes to identify/filter the resource. My understanding of annotations is that it is metadata that adds key-value pairs that cannot be used by Kubernetes for identifying/filtering the resource. I'm trying to wrap my head around the difference between annotations and labels.
0 kommentar(er)
